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<h1>Cluster Management</h1>

<h2>Why Web Services Clustering?</h2>

<p>Any production deployment of a server has to fulfil two basic needs. They
    are high availability and scalability. High availability refers to the
    ability to serve client requests by tolerating failures. Scalability is the
    ability to serve a large number of clients sending a large number of requests
    without a degradation of the performance. Almost all successful server
    products support the above two features to some extent.</p>

<p>Another requirement that pops up naturally with the above two features is
    the ability to manage clustered deployments from a single point. There is no
    exception when it comes to Web services servers. Many large scale enterprises
    are adapting to Web services as the de facto middleware standard. These
    enterprises have to process millions of transactions per day, or even more. A
    large number of clients, both human and computers, connect simultaneously to
    these systems and initiate transactions. Therefore, the servers hosting the
    Web services for these enterprises have to support that level of performance
    and concurrency. In addition, almost all the transactions happening in such
    enterprise deployments are critical to the business of the organization. This
    imposes another requirement for production ready Web services servers. That
    is to maintain very low downtime. </p>

<p>It is impossible to support that level of scalability and high
    availability from a single server despite how powerful the server hardware or
    how efficient the server software. Web services clustering is needed to solve
    this, which allows to deploy and manage several instances of identical Web
    services across multiple Web services servers running on different server
    machines.</p>

<p></p>

<h2>Cluster Management Component</h2>

<p>This cluster management component can be used to manage the entire
    Carbon cluster or individual cluster groups. You can perform the following
    operations on the entire cluster or on a selected cluster group.</p>
<ul>
    <li>Shut down</li>
    <li>Restart</li>
    <li>Switch to maintenance mode</li>
</ul>

<p>In addition to that, you can access the management console of each
    host in a cluster group and manage that host.</p>

<p></p>

<h2>Cluster Management User Interface</h2>

<p>Cluster Management user interface allows you to easily control the entire
    cluster or individual cluster groups.</p>

<h3>Managing the entire cluster</h3>

<p>Figure 1 shows the first page which will appear when you click on the
    Manage > Cluster menu item. This interface shows all existing cluster
    groups and you can perform the above mentioned operations such that
    it will afftect all listed cluster groups.</p>

<img src="images/cluster.png" alt="Managing all cluster groups" width="1014" height="535">

<p><strong>Figure 1 :</strong> Managing the entire cluster</p>

<p>You can move into the individual cluster group management user interface by clicking
    on the cluster group name.</p>

<h3>Managing a single cluster group</h3>

<p>Figure 2 shows the individual cluster group management user interface. It
    lists all hosts (nodes) in the cluster. You can perform the above
    mentioned operations such that it will afftect only for this particular
    cluster group.</p>

<img src="images/cluster_group.png" alt="Managing a single cluster group" width="1013" height="524">

<p><strong>Figure 2 :</strong> Managing a single cluster group</p>

<p>And also, you can use the "Management Console" link infront of each listed
    host to connect to the management console of that particular host. If that
    host doesn't have a management console (it only has a backend), "Connect
    to Backend" link can be used to connect to the backend of that host using the
    current Carbon UI.</p>

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